The present invention relates broadly to a survival device designed to be worn by individuals involved in recreational or work activities in which the possibility exists that the individual will be accidentally immersed in cold water. In particular, the present invention is a survival suit having flotation properties capable of supporting an adult, and which provides thermal protection to prevent hypothermia of the individual when immersed in cold water for a substantial length of time.
Commercial fishing boats, recreational and other water craft often are operated in relatively cold water. Additionally, off-shore drilling platforms are frequently located in severe cold water environments. Individuals engaged in such activities in cold water environments are subject to the potential dangers of being accidentally immersed in cold water for substantial periods of time before they are rescued. The greatest danger other than drowning in such circumstances is from the rapid loss of body heat, or hypothermia, which results in death. Generally the individual's heart will fail when the body cools to about 85 degrees F. or below.
Several factors are involved in determining the amount of time that one can survive in cold water. These factors include the survival procedure utilized. If the individual is required to tread water, the body loses heat at a much faster rate than if the individual remained motionless. Swimming also results in an increased rate of body heat loss. Other factors involved include the weight of the individual and the amount of body fat. As a general rule, the predicted survival time of an individual in water of 50 degrees F. averages between two and one-half to three hours,
It is desirable, therefore, to minimize the physical activity of the individual immersed in cold water, and to maximize the thermal protection against body heat loss. Certain regions of the body have higher rates of heat loss and must be thermally insulated. These areas include the head, the antero-lateral neck region where the carotid arteries connecting the heart to the head region are located, the sides of the thorax or chest region, the heart region of the thorax, and the groin region where blood and lymph vessels are near the skin surface. The thoracic-duct area of the back is also a high heat loss region. The thoracic duct is the largest lymphatic vessel in the body and is located along the vertebral column and serving tp convey lymph to the left subclavian vein where the lymph enters the circulatory system. To minimize the individual survival activity, flotation means must be provided to keep the individual afloat without physical exertion. Additionally, to minimize the dangers of hypothermia and maximize survival time in the water, it is desirable to provide effective thermal insulation for the high heat loss areas of the body.
Conventional life jackets typically have only flotation characteristics. The individual wearing such conventional jackets may assume a posture in the water that somewhat lessens heat loss. In this posture, the arms are held tightly to the sides of the chest with the legs together and knees drawn upward toward the chest. Although this posture may lessen the heat loss somewhat, it is highly inefficient and the survival time is not significantly increased.
Survival time has been increased somewhat in one prior art flotation jacket disclosed in U.S. Pat. No. 4,015,300 to Hayward et al. This prior art jacket has flotation material therein adequate to keep an adult afloat. A flap of waterproof insulating material is secured on the inside of the jacket proximate the bottom edge and can be released to wrap around the lower trunk of the wearer providing thermal protection in cold water. The flap is drawn between the wearer's legs and wrapped around the upper legs and thighs and secured to the outside of the flotation jacket. In this prior art jacket, although the high heat loss area in the groin region is covered, the only thermal insulation for the other high heat loss areas of the thorax is the insulative properties of the flotation material and jacket lining. Although the flap portion may prevent substantial amounts of water from entering the jacket in the area of the thighs, cold water may still find its way through the jacket zipper and arm portions into contact with the chest region resulting in a rapid heat loss from the thorax, particularly the sides of the chest. In addition, there may be some reluctance to wearing this prior art flotation jacket with the flap properly positioned about the upper legs and thighs and attached to the outside of the jacket since the flap provides a diaper-like external appearance. The prior art jacket may lose its effect if the wearer does not secure the flap about his thighs and groin area before he finds himself in the water. By this time, a substantial amount of water would enter the jacket, cooling the thorax region.
The present invention eliminates the disadvantages of the conventional prior art flotation jackets and the flotation jacket disclosed in the above mentioned U.S. patent in that it provides thermal protection for the major areas of heat loss from the body in addition to having flotation characteristics. In particular, the present invention is a survival suit having an outer jacket and an inner jacket. The inner jacket is attached to the inner lining of the outer jacket and is adapted to fit snugly about the torso of the body providing thermal protection for the major areas of heat loss of the thoracic anterior and dorsal regions. A crotch flap is provided that is positioned between the legs of the wearer and secured to the front of the inner jacket providing additional thermal protection for the groin area of the body. When the inner jacket is in place snugly about the torso it is entirely concealed from view by the outer jacket. The outer jacket presents an aesthetically pleasing look thereby encouraging the wearer of the survival suit to have the inner jacket in place while on board the water craft. The snug fit of the inner jacket minimizes cold water contact with the torso. In the event of penetration of a small amount of water into contact with the torso, the inner jacket serves to entrap an insulating layer of water that is heated by body heat and to minimize the exchange of cold water with the heated layer. The high heat loss areas of the torso are thereby thermally insulated.